1. Field of the Invention
This invention relates to a method for manufacturing a glass container and an apparatus therefor, and more particularly to a method for manufacturing a seamless glass container used for a display device and an apparatus therefor.
2. Discussion of the Background
Manufacturing of a container used as an envelope or a getter box for a display device such as a fluorescent display device has been conventionally carried out according to such an assembling procedure as shown in FIGS. 4(a) to 4(e).
More particularly, first a glass plate of a large size is cut into a bar-like glass piece 31 of predetermined dimensions and a rectangular glass piece 32 of a predetermined dimensions, as shown in FIG. 4(a). Then, the bar-like glass piece 31 is coated on one surface thereof with a seal glass material 33, followed by calcination as shown in FIG. 4(b). Likewise, the rectangular glass piece 32 is coated on an outer peripheral edge thereof with the seal glass 33, followed by calcination.
Then, a frame of a shape corresponding to an outer configuration of the rectangular glass piece 32 is manufactured. This is carried out by cutting the bar-like glass piece 31 into two long-length glass pieces 31a of predetermined dimensions and two short-length glass pieces 31b of predetermined dimensions as shown in FIG. 4(c). Then, the long-length glass pieces 31a and short-length glass pieces 31b are combined with each other to form a frame 34 as shown in FIG. 4(d).
Thereafter, the frame 34 thus formed is arranged on the outer peripheral edge of the glass piece 32 and then the frame 34 and glass piece 32 are fixed together by means of a fixture while being kept aligned with each other, followed by calcination. This permits melting of the seal glass 33, leading to fixing between the frame 34 and the glass piece 32, so that a glass container 35 may be finished which has an opening 35a formed on one surface thereof as shown in FIG. 4(e).
Unfortunately, it was found that the assembling procedure shown in FIGS. 4(a) to 4(e) has problems.
More particularly, the assembling procedure uses the seal glass for bonding the glass pieces 31a and 31b and the glass piece 32 to each other. The seal glass generates foam, resulting in possibly causing leakage through the glass container.
Another disadvantage of the assembling procedure is that the procedure requires three members different in size or the glass pieces 31a, 31b and 32, to thereby increase the number of times of change-over of a cutting machine and render an installation therefor complicated and large-sized.
A further problem is that use of the seal glass 33 causes the seal glass melted to be adhered to a surface of the glass pieces.
Also, the procedure increases the number of steps for the assembling, to thereby increase the manufacturing cost.
Still another problem of the procedure increases the number of tools depending on a production capacity.
Another method for manufacturing a glass container by means of a forming die made of a carbon material having a coefficient of expansion similar to glass is also proposed as disclosed in Japanese Patent Publication No. 64572/1995.
However, the proposed method using the forming die has a disadvantage that the forming die is highly worn with an increase in softening temperature of glass, to thereby be deteriorated in durability thereof, because it is made of carbon. Also, it encounters another problem of rendering uniform heating of whole glass highly difficult because the glass is subject to repeated heating and cooling while being placed in a continuous oven or furnace. In particular, processing of glass increased in softening point causes time to be required for heating top and lower molds of the forming die, so that energy efficiency is substantially deteriorated and much time is required for formation of the glass container.